The visualization of image data of the inner surface of hollow organs, for example a blood vessel or an intestine, or sections thereof, often is used to detect bumps of these inner surfaces. These bumps can be the result of, for example, growths such as polyps or lesions. A person examining the inner surface of a hollow organ for bumps therefore wants to ensure that no bump, from which dangerous symptoms may be inferred, remains unnoticed.
For the purposes of visualization, it is possible to produce so-called multi-planar reconstructions, i.e. slice images, in a so-called two-dimensional workflow of volume data records of a volume data record region comprising a hollow organ. The slices are usually orthogonal with respect to the patient axes or to the axes of a hollow organ or a body comprising the hollow organ. The multi-planar reconstructions are examined for suspicious structures and possibly marked thereafter. Subsequently, the marked location of the image data record can be examined and processed further using three-dimensional displays, e.g. using the volume rendering technique or a surface shaded display.
As an alternative to the two-dimensional workflow, the reverse path can be undertaken in the three-dimensional workflow: the image data of a hollow organ filled with a contrast agent, for example air or carbon dioxide, are segmented. Subsequently, a so-called virtual flight is carried out through the hollow organ. In the process, the hollow organ surface is displayed by means of a surface shaded display. A suspicious location is marked by a user, and the workstation immediately displays identical positions in one or more multi-planar reconstructions of the volume data record. The suspicious location is made visible with the aid of this display.
Using the two-dimensional workflow, different data records, for example those which were generated in the prone and dorsal positions of a patient, can be examined very rapidly. By contrast, the advantage of the three-dimensional workflow is that significantly more bumps can be found. However, due to the presence of a multiplicity of usual bumps in hollow organs, e.g. the intestinal folds in the case of a scan of the intestine, this is also connected to increased time expenditure.
In order to reduce this disadvantage in terms of speed, so-called virtual dissection can be used. To put it simply, the hollow organ is in this case considered to be a tube which is cut open in the longitudinal direction, spread open and displayed in the plane of a screen. The visualization of bumps is found to be particularly difficult in the case of virtual dissection because it in turn is a purely two-dimensional form of display.
US 2006/0221074 A1, the entire contents of which are hereby incorporated herein by reference, illustrates such a virtual dissection. Moreover, this publication shows how the surface of a hollow organ can be scanned virtually using a so-called ray casting method. Furthermore, US 2008/0055308 A1 describes that such a ray casting is particularly effective in recognizing lesions and objects hidden behind bumps when the location of the ray caster, that is to say a sending unit (referred to as a camera in this document), is displaced along the profile of the hollow organ. This can be performed both in a three-dimensional image and in the display of the virtual dissection.